Gadolinium-based contrast agents are used to improve visibility of internal structures when a patient undergoes a magnetic resonance imaging (MRI) procedure. These agents are typically administered intravenously immediately prior to imaging. One important contrast agent is gadofosveset trisodium monohydrate (Ablavar®) (structure shown below).

Because gadofosveset trisodium monohydrate is administered intravenously, it is important to provide the agent in a pharmaceutically acceptable formulation. Further, there is a need to reduce the number of chromatographic steps used to obtain pharmaceutically acceptable purity for the contrast agent, as additional steps can reduce yields and increase cost. This application addresses these needs and others.